Method for producing organic electroluminescent display device comprising polydiacetylene layer

ABSTRACT

An organic EL display device ( 100 ) includes a plurality of pixels, and also includes an element substrate including organic EL elements ( 3 ) respectively located in the plurality of pixels and a bank layer ( 48 ) defining each of the pixels; and a thin film encapsulation structure ( 10 ) covering the plurality of pixels. The thin film encapsulation structure includes a first inorganic barrier layer ( 12 ) and an organic barrier layer ( 14 ) in contact with a top surface or a bottom surface of the first inorganic barrier layer. The plurality of pixels include a red pixel, a green pixel and a blue pixel. The organic EL display device further includes a polydiacetylene layer ( 52 ) selectively provided on a second inorganic barrier layer ( 16 ) of the thin film encapsulation structure on the blue pixel and exhibiting a blue color. The polydiacetylene layer is a polymer of 10,12-pentacosadiynoic acid.

TECHNICAL FIELD

The present invention relates to an organic EL display device and amethod for producing the same.

BACKGROUND ART

Organic EL (Electroluminescence) display devices start being put intopractical use. One feature of an organic EL display device isflexibility thereof. Such an organic EL display device includes, in eachof pixels, at least one organic EL element (Organic Light EmittingDiode: OLED) and at least one TFT (Thin Film Transistor) controlling anelectric current to be supplied to the at least one OLED. Hereinafter,an organic EL display device will be referred to as an “OLED displaydevice”. Such an OLED display device including a switching element suchas a TFT or the like in each of OLEDs is called an “active matrix OLEDdisplay device”. A substrate including the TFTs and the OLEDs will bereferred to as an “element substrate”.

An OLED (especially, an organic light emitting layer and a cathodeelectrode material) is easily influenced by moisture to be deterioratedand to cause display unevenness. One technology developed to provide anencapsulation structure that protects the OLED against moisture whilenot spoiling the flexibility of the OLED display device is a thin filmencapsulation (TEE) technology. According to the thin film encapsulationtechnology, an inorganic barrier layer and an organic barrier layer arestacked alternately to allow such thin films to provide a sufficientlyhigh level of water vapor barrier property. From the point of view ofthe moisture-resistance reliability of the OLED display device, such athin film encapsulation structure is typically required to have a WVTR(Water Vapor Transmission Rate) lower than, or equal to, 1×10⁻⁴g/m²/day.

A thin film encapsulation structure used in OLED display devicescommercially available currently includes an organic barrier layer(polymer barrier layer) having a thickness of about 5 μm to about 20 μm.Such a relatively thick organic barrier layer also has a role offlattening a surface of the element substrate. However, such a thickorganic barrier layer involves a problem that the bendability of theOLED display device is limited.

Patent Document No. 1 discloses a thin film encapsulation structureincluding a first inorganic material layer, a first resin member and asecond inorganic material layer provided on the element substrate inthis order, with the first inorganic barrier layer being closest to theelement substrate. In this thin film encapsulation structure, the firstresin member is present locally, more specifically, in the vicinity of aprotruding portion of the first inorganic material layer (firstinorganic material layer covering the protruding portion). According toPatent Document No. 1, since the first resin member is present locally,more specifically, in the vicinity of the protruding portion, which maynot be sufficiently covered with the first inorganic material layer,entrance of moisture or oxygen via the non-covered portion issuppressed. In addition, the first resin member acts as an underlyinglayer for the second inorganic material layer. Therefore, the secondinorganic material layer is properly formed and properly covers a sidesurface of the first inorganic material layer with an expectedthickness. The first resin member is formed as follows. An organicmaterial heated and gasified to be mist-like is supplied onto an elementsubstrate, maintained at a temperature lower than, or equal to, roomtemperature. The organic material is condensed and put into liquid dropson the substrate. The organic material in the liquid drops moves on thesubstrate by a capillary action or a surface tension to be presentlocally, more specifically, at a border between a side surface of theprotruding portion of the first inorganic barrier layer and a surface ofthe substrate. Then, the organic material is cured to form the firstresin member at the border. Patent Document No. 2 also discloses an OLEDdisplay device including a similar thin film encapsulation structure.

The thin film encapsulation structure, described in each of PatentDocuments Nos. 1 and 2, including an organic barrier layer formed of aresin member that is present locally does not include a thick organicbarrier layer, and therefore, is considered to improve the bendabilityof the OLED display device.

In the meantime, it has been attempted to improve the colorreproducibility of the OLED display device. For example, Patent DocumentNo. 3 discloses an optical film capable of suppressing a color fromlooking different in accordance with the observation direction, and anOLED display device including the same.

CITATION LIST Patent Literature

-   -   Patent Document No. 1: WO2014/196137    -   Patent Document No. 2: Japanese Laid-Open Patent Publication No.        2016-39120    -   Patent Document No. 3: Japanese Laid-Open Patent Publication No.        2015-102811    -   Patent Document No. 4: WO2001/39554

SUMMARY OF INVENTION Technical Problem

However, the optical film has a problem of not being capable ofoptimizing the color display characteristic of each of pixels.Especially in an OLED display device having a microcavity structure, anorganic EL layer (e.g., organic light emitting layer) has a thicknessadjusted such that an optimal resonation is provided in each of colorsof pixels (see, for example, Patent Document No. 4). In this case, thethickness of the organic EL layer is optimized in accordance with thecolor provided by each pixel. Therefore, the thickness of the organic ELlayer is thinnest in a blue pixel. For this reason, the thickness of theorganic EL layer in the blue pixel is more varied than that in a greenpixel and a red pixel. As a result, the color purity of blue isdecreased, which may undesirably decrease the color reproducibility ofthe OLED display device.

In addition, the above-described thin film encapsulation structureincluding the organic barrier layer formed of a resin located locallyhas concaved and convexed portions at a surface thereof, and therefore,has a problem of not easily allowing an optical film to be attachedthereto uniformly.

The present invention has an object of providing an organic EL displaydevice having an improved color reproducibility of a blue pixel and amethod for producing the same.

Solution to Problem

An organic EL display device according to an embodiment of the presentinvention is an organic EL display device including a plurality ofpixels. The organic EL display device includes an element substrateincluding a substrate, a plurality of organic EL elements supported bythe substrate and respectively located in the plurality of pixels, and abank layer defining the plurality of pixels; and a thin filmencapsulation structure covering the plurality of pixels. The thin filmencapsulation structure includes a first inorganic barrier layer and anorganic barrier layer in contact with a top surface or a bottom surfaceof the first inorganic barrier layer. The plurality of pixels include ared pixel, a green pixel and a blue pixel. The organic EL display devicefurther includes a polydiacetylene layer, selectively provided on thethin film encapsulation structure on the blue pixel and exhibiting ablue color. The polydiacetylene layer is a polymer of 10,12-pentacosadiynoic acid.

In an embodiment, the organic barrier layer-included in the thin filmencapsulation structure is in contact with the top surface of the firstinorganic barrier layer and includes a plurality of solid portionsdistributed discretely. The thin film encapsulation structure furtherincludes a second inorganic barrier layer in contact with the topsurface of the first inorganic barrier layer and top surfaces of theplurality of solid portions of the organic barrier layer. Thepolydiacetylene layer is formed on the second inorganic barrier layer.

In an embodiment, the polydiacetylene layer is semiconductive.

In an embodiment, the polydiacetylene layer has a specific resistancesmaller than, or equal, to, 1×10⁻¹ Ωcm.

In an embodiment, the organic EL display device further includes anultraviolet absorbing layer located on the polydiacetylene layer.

In an embodiment, the first inorganic barrier layer is formed of siliconnitride. In an embodiment, the second inorganic barrier layer is alsoformed of silicon nitride.

In an embodiment, the polydiacetylene layer has a thickness of 0.5 μm orgreater and 2.0 μm or less.

In an embodiment, the polydiacetylene layer provides a transmissionspectrum of blue light in which the blue light has a peak wavelength inthe range of 460 nm or longer and about 470 nm or shorter.

In an embodiment, the polydiacetylene layer has a transmittance for theblue light higher than, or equal to, 80% at the peak wavelength thereof.

A method for producing an organic El display device according to anembodiment of the present invention is a method for producing theorganic EL display device described in any of the above. A step offorming the polydiacetylene layer includes the steps of: after the thinfilm encapsulation structure is formed, depositing 10,12-pentacosadiynoic acid on the thin film encapsulation structure bymask vapor deposition; and irradiating the 10, 12-pentacosadiynoic acidwith an electron beam or ultraviolet, rays.

In an embodiment, the step of forming the thin film encapsulationstructure includes the step of forming a silicon nitride layer. Afterthe silicon nitride layer is formed, the 10, 12-pentacosadiynoic acid isdeposited by the mask vapor deposition without exposing the siliconnitride layer to the atmosphere.

In an embodiment, the step of forming the thin film encapsulationstructure includes the steps of preparing, in a chamber, the elementsubstrate on which the first inorganic barrier layer is formed,supplying a vapor-like or mist-like photocurable resin into the chamber,condensing the photocurable resin on the first inorganic barrier layerto form a liquid film, irradiating the liquid film of the photocurableresin with light to form a photocured resin layer, and partially ashingthe photocurable photocured resin layer to form the organic barrierlayer.

In an embodiment, the step of forming the organic barrier layer isperformed by spraying, spin-coating, slit-coating, screen printing orink-jetting.

Advantageous Effects of Invention

An embodiment of the present invention provides an organic EL displaydevice having an improved color reproducibility of a blue pixel and amethod for producing the same.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a schematic partial cross-sectional view of an activeregion of an OLED display device 100 according to an embodiment of thepresent invention, and FIG. 1(b) is a partial cross-sectional view of aTFE structure 10 formed on an OLED 3.

FIG. 2 is a plan view schematically showing a structure of the OLEDdisplay device 100 according to embodiment 1 of the present invention.

FIG. 3(a) through FIG. 3(c) are each a schematic cross-sectional view ofthe OLED display device 100; FIG. 3(a) is a cross-sectional view takenalong line 3A-3A′ in FIG. 2, FIG. 3(b) is a cross-sectional view takenalong line 3B-3B′ in FIG. 2, and FIG. 3(c) is a cross-sectional viewtaken along line 3C-3C′ in FIG. 2.

FIG. 4(a) is an enlarged view of a portion including a particle P shownin FIG. 3(a), FIG. 4(b) is a schematic plan view showing the sizerelationship among the particle P, a first inorganic barrier layer (SiNlayer) covering the particle P, and an organic barrier layer; and FIG.4(c) is a schematic cross-sectional view of the first inorganic barrierlayer covering the particle P.

FIG. 5 is a plan view schematically showing a bank layer 48 included inthe OLED display device 100.

FIG. 6 provides cross-sectional views schematically showing a pixel andthe bank layer 48 included in the OLED display device 100; FIG. 6(a) isa cross-sectional view of a blue pixel taken long line 6A-6A′ in FIG. 5,and FIG. 6(b) is a cross-sectional view of a green pixel taken long line6B-6B′ in FIG. 5.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an OLED display device and a method for producing the sameaccording to embodiments of the present invention will be described withreference to the drawings. The embodiments of the present invention arenot limited to the embodiments that are described below as examples. Forexample, an organic EL display device according to an embodiment of thepresent invention may include, for example, a glass substrate instead ofa flexible substrate.

First, with reference to FIG. 1(a) and FIG. 1(b), a basic structure ofan OLED display device 100 according to an embodiment of the presentinvention will be described. FIG. 1(a) is a schematic partialcross-sectional view of an active region of the OLED display device 100according to an embodiment of the present invention. FIG. 1(b) is apartial cross-sectional view of a TFE structure 10 formed on an OLED 3.

The OLED display device 100 includes a plurality of pixels, and each ofthe pixels includes at least one organic EL element (OLED). Herein, astructure corresponding to one OLED will be described for the sake ofsimplicity.

As shown in FIG. 1(a), the OLED display device 100 includes a flexiblesubstrate (hereinafter, may be referred to simply as a “substrate”) 1, acircuit (backplane) 2 formed on the substrate 1 and including a TFT, theOLED 3 formed on the circuit 2, and the TFE structure 10 formed on theOLED 3. The OLED 3 is, for example, of a top emission type. An uppermostportion of the OLED 3 is, for example, an upper electrode or a cap layer(refractive index adjusting layer). An optional polarizing plate 4 islocated on the TFE structure 10.

The substrate 1 is, for example, a polyimide film having a thickness of15 μm. The circuit 2 including the TFT has a thickness of, for example,4 μm. The OLED 3 has a thickness of, for example, 1 μm. The TFEstructure 10 has a thickness of, for example, less than, or equal to,1.5 μm.

FIG. 1(b) is a partial cross-sectional view of the TFE structure 10formed on the OLED 3. The TFE structure 10 includes a first inorganicbarrier layer (e.g., SiN layer) 12, an organic barrier layer (e.g.,acrylic resin layer) 14, and a second inorganic barrier layer (e.g., SiNlayer) 16. The first inorganic barrier layer 12 is formed immediately onthe OLED 3. The organic barrier layer 14 is in contact with a topsurface of the first inorganic barrier layer 12, and includes aplurality of solid portions distributed discretely. The second inorganicbarrier layer 16 is in contact with the top surface of the firstinorganic barrier layer 12 and top surfaces of the plurality of solidportions of the organic barrier, layer 14. The organic barrier layer 14is transparent (having a visible light transmittance of 95% or higherwhen having a thickness of 1 μm).

For example, the first inorganic barrier layer 12 and the secondinorganic barrier layer 16 are each an SiN layer (e.g., Si₃N₄ layer)having a thickness of, for example, 400 nm. The thicknesses of the firstinorganic barrier layer 12 and the second inorganic barrier layer 16 areeach independently 200 nm or greater and 1000 nm or less. The TFEstructure 10 has a thickness of, preferably, 400 nm or greater and lessthan 2 μm, and more preferably, 400 nm or greater and less than 1.5 μm.The thickness of the organic barrier layer 14, which depends on the sizeof a protruding portion at the surface of the first inorganic barrierlayer 12 or the size of the particle, may be about 1 μm at the maximum.The thickness of the organic barrier layer 14 is typically 200 nm orgreater and 500 nm or less.

The TFE structure 10 is formed to protect an active region (see anactive region R1 in FIG. 2) of the OLED display device 100. As describedabove, the TFE structure 10 includes the first inorganic barrier layer12, the organic barrier layer 14 and the second inorganic barrier layer16 provided in this order on at least the active region, with the firstinorganic barrier layer 12 being closest to the OLED 3. The organicbarrier layer 14 is not present as a film covering the entirety of theactive region, but includes an opening. A portion of the organic barrierlayer 14 excluding the opening, more specifically, a portion where theorganic film is actually present, will be referred to as a “solidportion”. The opening (may also be referred to as a “non-solid portion”)does not need to be enclosed by the solid portion, and the openingincludes a cut-out portion or the like. In the opening, the firstinorganic barrier layer 12 and the second inorganic barrier layer 16 arein direct-contact with each other. The opening of the organic barrierlayer 14 includes at least an opening formed to enclose the activeregion, and the active region is completely enclosed by the portion inwhich the first inorganic barrier layer 12 and the second inorganicbarrier layer 16 are in direct contact with each other (hereinafter,such a portion will be referred to as an “inorganic barrier layer joint,portion”).

With reference to FIG. 2 through FIG. 6, a structure of an OLED displaydevice and a method for producing the same according to an embodiment ofthe present invention will be described.

FIG. 2 is a schematic plan view of the OLED display device 100 accordingto an embodiment of the present invention.

The OLED display device 100 includes the flexible substrate 1, thecircuit (backplane) 2 formed on the substrate 1, a plurality of theOLEDs 3 formed on the circuit 2, and the TFE structure 10 formed on theOLEDs 3. A layer including the plurality of OLEDs 3 may be referred toas an “OLED layer 3”. The circuit 2 and the OLED layer 3 may share apart of components. The optional polarizing plate (see reference sign 4in FIG. 1) may further be located on the TFE structure 10. In addition,for example, a layer having a touch panel function may be locatedbetween the TFE structure 10 and the polarizing plate. Namely, the OLEDdisplay device 100 may be altered to a display device including anon-cell type touch panel.

The circuit 2 includes a plurality of TFTs (not shown), and a pluralityof gate bus lines (not shown) and a plurality of source bus lines (notshown) each connected to either one of the plurality of TFTs (notshown). The circuit 2 may be a known circuit that drives the pluralityof OLEDs 3. The plurality of OLEDs 3 are each connected with either oneof the plurality of TFTs included in the circuit 2. The OLEDs 3 may beknown OLEDs.

The OLED display device 100 further includes a plurality of terminals 38located in a peripheral region R2 outer to the active region (regionenclosed by the dashed line in FIG. 2) R1, where the plurality of OLEDs3 are located, and also includes a plurality of lead wires 30 eachconnecting either one of the plurality of terminals 38 and either one ofthe plurality of gate bus lines or either one of the plurality of sourcebus lines to each other. The TFE structure 10 is formed on the pluralityof OLEDs 3 and on portions of the plurality of lead wires 30, theportions being closer to the active region R1. Namely, the TFE structure10 covers the entirety of the active region R1 and is also selectivelyformed on the portions of the plurality of lead wires 30 that are closerto the active region R1. Neither portions of the plurality of lead wires30 that are closer to the terminals 38, nor the terminals 38, arecovered with the TFE structure 10.

Hereinafter, an example in which the lead wires 30 and the terminals 38are integrally formed of the same conductive layer will be described.Alternatively, the lead wires 30 and the terminals 38 may be formed ofdifferent conductive layers (encompassing stack structures).

Now, with reference to FIG. 3(a) through FIG. 3(c), the TFE structure 10of the OLED display device 100 will be described. FIG. 3(a) is across-sectional view taken along line 3A-3A′ in FIG. 2. FIG. 3(b) is across-sectional view taken along line 3B-3B′ in FIG. 2. FIG. 3(c) is across-sectional view taken along line 3C-3C′ in FIG. 2.

As shown in FIG. 3(a) and FIG. 3(b), the TFE structure 10 includes thefirst inorganic barrier layer 12 formed on the OLED 3, the organicbarrier layer 14, and the second inorganic barrier layer 16 in contact,with the first inorganic barrier layer 12 and the organic barrier layer14. The first inorganic barrier layer 12 and the second inorganicbarrier layer 16 are each, for example, an SiN layer, and are eachselectively formed in a predetermined region by plasma CVD by use of amask so as to cover the active region R1. In general, a surface of alayer formed by a thin film deposition method (e.g., CVD, sputtering,vacuum vapor deposition) reflects a stepped portion in an underlyinglayer. The organic barrier layer (solid portion) 14 is formed only inthe vicinity of the protruding portion at the surface of the firstinorganic barrier layer 12.

FIG. 3(a) is a cross-sectional view taken along line 3A-3A′ in FIG. 2,and shows a portion including a particle P. The particle P is amicroscopic, dust particle generated during the production of the OLEDdisplay device, and is, for example, a microscopic piece of brokenglass, a metal particle or an organic particle. Such a particle P isgenerated especially easily in the case where mask vapor deposition isused.

As shown in FIG. 3(a), the organic barrier layer (solid portion) 14 mayinclude a portion 14 b formed in the vicinity of the particle P. Areason for this is that an acrylic monomer supplied after the firstinorganic barrier layer 12 is formed is condensed and present locally,more specifically, in the vicinity of a surface of a first inorganicbarrier layer 12 a on the particle P (the surface has a tapering anglelarger than 90 degrees). The organic barrier layer 14 includes theopening (non-solid portion) on a flat portion of the first inorganicbarrier layer 12.

Now, with reference to FIG. 4(a) through FIG. 4(c), a structure of theportion including the particle P will be described. FIG. 4(a) is anenlarged view of the portion including the particle P shown in FIG.3(a). FIG. 4(b) is a schematic plan view showing the size relationshipamong the particle P, the first inorganic barrier layer (SiN layer) 12covering the particle P, and the organic barrier layer 14. FIG. 4(c) isa schematic cross-sectional view of the first inorganic barrier layercovering the particle P.

As shown in FIG. 4(c), in the case where the particle (having adiameter, for example, longer than, or equal to, 1 μm) P is present, acrack (defect) 12 c may be formed in the first inorganic barrier layer12. As described below, this is considered to be caused by impingementof the SiN layer 12 a growing from a surface of the particle P and anSiN layer 12 b growing from a flat portion of a surface of the OLED 3.In the case where such a crack 12 c is present, the level of barrierproperty of the TFE structure 10 is decreased.

In the TFE structure 10 of the OLED display device 100, as shown in FIG.4(a), the organic barrier layer 14 is formed to fill the crack 12 c ofthe first inorganic barrier layer 12, and a surface of the organicbarrier layer 14 couples the surface of the first inorganic barrierlayer 12 a on the particle P and a surface of the first inorganicbarrier layer 12 b on the flat portion of the OLED 3 to each othercontinuously and smoothly. The organic barrier layer 14 is formed bycuring a photocurable resin in a liquid state as described below, andtherefore, has a recessed surface formed by a surface tension. In thisstate, the photocurable resin exhibits a high level of wettability tothe first inorganic barrier layer 12. If the level of wettability of thephotocurable resin to the first inorganic barrier layer 12 is low, thesurface of the organic barrier layer 14 may protrude, instead of beingrecessed. The organic barrier layer 14 may also be formed as a thin filmon the surface of the first inorganic barrier layer 12 a on the particleP.

The organic barrier layer (solid portion) 14 having the recessed surfacecouples the surface of the first inorganic barrier layer 12 a on theparticle P and the surface of the first inorganic barrier layer 12 b onthe flat portion to each other continuously and smoothly. Therefore, thesecond inorganic barrier layer 16 formed thereon is a fine film with nodefect. As can be seen, even if the particle P is present, the organicbarrier layer 14 keeps high the level of barrier property of the TFEstructure 10.

As shown in FIG. 4(b), the organic barrier layer 14 (solid portion) isformed in a ring shape around the particle P. Where the particle P has adiameter (equivalent circle diameter) of about 1 μm as seen in adirection normal to the surface of the OLED 3, the ring-shaped solidportion has a diameter (equivalent circle diameter) D₀ that is, forexample, longer than, or equal to, 2 μm.

In this example, the organic barrier layer 14 is formed only in adiscontinuous portion in the first inorganic barrier layer 12 formed onthe particle P, and the particle P is already present before the firstinorganic barrier layer 12 is formed on the OLED 3. Alternatively, theparticle P may be present on the first inorganic barrier layer 12. Inthis case, the organic barrier layer 14 is formed only at the border,namely, in a discontinuous portion, between the first inorganic barrierlayer 12 and the particle P on the first inorganic barrier layer 12, andthus maintains the level of barrier property of the TFE structure 10like in the above-described case. The organic barrier layer 14 may alsobe formed as a thin film on the surface of the first inorganic barrierlayer 12 a on the particle P, or on the surface of the particle P. Inthis specification, the expression that “the organic, barrier layer 14is present in the vicinity of the particle P” encompasses all theseforms.

The organic barrier layer (solid portion) 14 is not limited to beingformed as in the example of FIG. 3(a), and may be formed only in thevicinity of the protruding portion at the surface of the first inorganicbarrier layer 12 for substantially the same reason as that describedabove. Examples of other regions where the organic barrier layer (solidportion) 14 may be formed will be described below.

Now, with reference to FIG. 3(b), a structure of the TFE structure 10 onthe lead wires 30 will be described. FIG. 3(b) is a cross-sectional viewtaken along line 3B-3B′ in FIG. 2, more specifically, is across-sectional view of portions 32 of the lead wires 30, the portions32 being closer to the active region R1.

As shown in FIG. 3(b), the organic barrier layer (solid portion) 14includes a portion 14 c formed in the vicinity of each of the protrudingportions at the surface of the first inorganic barrier layer 12, theprotruding portions reflecting the cross-sectional shape of the portions32 of the lead wires 30.

The lead wires 30 are patterned by the same step as that, of, forexample, the gate bus lines or the source bus lines. Therefore, in theexample described below, the gate bus lines and the source bus linesformed in the active region R1 also have the same cross-sectionalstructure as that of the portions 32 shown m FIG. 3(b), of the leadwires 30, closer to the active region R1. It should be noted thattypically, a flattening layer is formed on the gate bus lines and thesource bus lines formed in the active region R1, and thus no steppedportion is formed at the surface of the first inorganic barrier layer 12on the gate bus lines and the source bus lines.

The portions 32 of the lead wires 30 may each have, for example, aforward tapering side surface portion (inclining side surface portion)having a tapering angle smaller than 90 degrees. In the case where thelead wires 30 each include the forward tapering side surface portion,formation of defects in the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 formed on the lead wires 30 isprevented. Namely, the moisture-resistance reliability of the TFEstructure 10 is improved. The tapering angle of the forward taperingside surface portion is preferably smaller than, or equal to, 70degrees.

The active region R1 of the OLED display device 100, except for theregions where the organic barrier layer 14 is selectively formed, issubstantially covered with the inorganic barrier layer joint portion, inwhich the first inorganic barrier layer 12 and the second inorganicbarrier-layer 16 are in direct contact with each other. Therefore, itdoes not occur that the organic barrier layer 14 acts as a moistureentrance route to allow the moisture to reach the active region R1 ofthe OLED display device.

The OLED display device 100 according to an embodiment of the presentinvention is preferably usable for, for example, medium- to small-sizedhigh-definition smartphones and tablet: terminals. In a medium- tosmall-sized (e.g., 5.7-inch) high-definition (e.g., 500 ppi) OLEDdisplay device, it is preferred that the lines (encompassing the gatebus lines and the source bus lines) in the active region R1 have across-sectional shape, in a direction parallel to a line width directionthereof, close to a rectangle (side surfaces of the lines have atapering angle of about 90 degrees) in order to have a sufficiently lowresistance with a limited line width. Therefore, in order to form thelines having a low resistance, the tapering angle of the forwardtapering side surface portion TSF may be larger than 70 degrees andsmaller than 90 degrees, or the tapering angle of the lines may be about90 degrees in the entire length of the lines with no forward taperingside surface portion TSF being provided.

Now, FIG. 3(c) will be referred to. FIG. 3(c) is a cross-sectional viewof a region where the TFE structure 10 is not formed. In this region,the terminals 38 have the same cross-sectional structure as that ofportions 36 of the lead wires 30 shown in FIG. 3(c). The portions 36 ofthe lead wires 30 shown in FIG. 3(c) may have a tapering angle of, forexample, 90 degrees.

Now, with reference to FIG. 5 and FIG. 6, the organic barrier layer 14formed in the vicinity of a bank structure BS will be described. Theorganic barrier layer (solid portion) 14 is also formed in the vicinityof a protruding portion at the surface of the first inorganic barrierlayer 12, the protruding portion being used to form the bank structureBS.

FIG. 5 is a plan view schematically showing the plurality of pixels anda bank layer 48 included in the OLED display device 100. The OLEDdisplay device 100 includes red pixels R, green pixels G and blue pixelsB. In this example, the pixels of the three primary colors are arrayedin stripes. The pixels are not limited to being arrayed in this manner.FIG. 6(a) is a cross-sectional view of a blue pixel taken along line6A-6A′ in FIG. 5. FIG. 6(b) is a cross-sectional view of a green pixeltaken along line 6B-6B′ in FIG. 5.

As shown in FIG. 6(a), the OLED display device 100 further includes thebank structure BS defining the plurality of pixels. The bank layer BShas an inclining surface enclosing each of the plurality of pixels. Theplurality of solid portions of the organic barrier layer 14 include apixel periphery solid portion 14 a extending on the first inorganicbarrier layer 12 from an inclining surface to a peripheral area in thepixel.

As shown in FIG. 6(a), the bank structure BS includes the bank layer(may be referred to also as a “PDL (Pixel Defining Layer”) 48 formed ofan insulating material. The bank layer 48 is formed between a lowerelectrode 42 and an organic layer 44 of the OLED 3. As shown in FIG.6(a), the OLED 3 includes the lower electrode 42, the organic layer 44formed on the lower electrode 42, and an upper electrode 46 formed onthe organic layer 44. In this example, the lower electrode 42 and theupper electrode 46 respectively act as an anode and a cathode of theOLED 3. The upper electrode 46 is a common electrode formed for theentirety of the pixels in the active region. By contrast, the lowerelectrode (pixel electrode) 42 is formed for each of the pixels. In thestructure in which the bank layer 48 is present between the lowerelectrode 42 and the organic layer 44, no holes are injected from thelower electrode 42 into the organic layer 44. Therefore, the regionwhere the bank layer 48 is present does not act as a pixel Pix. For thisreason, the bank layer 48 defines an outer perimeter of the pixel Pix.

As shown in FIG. 5, the pixels Pix are respectively defined by openingsin the bank layer 48. The bank layer 48 is formed to be, for example,lattice-shaped. A side surface of each of the openings of the bank layer48 has an inclining surface including the forward tapering side surfaceportion TSF. The inclining surface of the bank layer 48 encloses thecorresponding pixel. The bank layer 48 is formed of, for example, aphotosensitive resin (e.g., polyimide or acrylic resin). The bank layer48 has a thickness of, for example, 1 μm to 2 μm. The inclining surfaceof the bank layer 48 is inclined at an inclination angle θb that issmaller than, or equal to, 60 degrees. If the inclination angle θb ofthe inclining surface of the bank layer 48 is larger than 60 degrees, adefect may be caused in layers located on the bank layer 48. The layerslocated on the bank layer 48 (including, for example, the organic layer44, the upper electrode 46, the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16) may be included in the bank structureBS. The layers included in the bank structure BS may each have aninclining surface enclosing each of the plurality of pixels. In the casewhere the layers formed on the bank layer 48 are all thinner than thebank layer 48, the inclining surface of the bank structure BS isconsidered to have an inclination angle substantially equal to theinclination angle θb of the inclining surface of the bank layer 48. Thefirst inorganic barrier layer 12 is included in the bank structure BS,and has the inclining surface S12 enclosing each of the plurality ofpixels. The organic barrier layer (solid portion) 14 includes the pixelperiphery solid portion 14 a extending on the first inorganic barrierlayer 12 from the inclining surface S12 to a peripheral area in thepixel.

In the case where the pixel periphery solid portion 14 a is formed, asdescribed in PCT/JP2017/046472, an OLED display device having a higherfront luminance and a higher directivity than those of a conventionalOLED display device is provided. The entirety of the disclosure ofPCT/JP2017/046472 is incorporated herein by reference.

In a central area of each pixel, the organic barrier layer 14 is formedonly in a discontinuous portion formed in the first inorganic barrierlayer 12 by the particle P. Namely, the organic barrier layer 14 is notpresent in a region, of the central area of the pixel, where no particleP is present. The OLED display device with no particle P does notinclude the organic barrier layer in the central area of the pixel. Theparticle P has a size (equivalent spherical diameter) of typically 0.3μm or longer and 5 μm or shorter. A substrate of G4.5 (730 mm×920 mm)may include, for example, several tens to about 100 particles. One OLEDdisplay device (active region) may include approximately severalparticles. Needless to say, there are OLED display devices with noparticle P. The organic barrier layer 14 is formed of, for example, aphotocured resin formed by curing a photocurable resin. A portion wherethe photocurable resin is actually present is referred to as a “solidportion”. As described above, the organic barrier layer 14 (solidportion) is selectively formed only in the vicinity of the protrudingportion at the surface of the first inorganic barrier layer 12.

In the case where there is a particle P in the central area of thepixel, the organic barrier layer 14 is formed in a discontinuous portionformed by the particle P. As described above with reference to FIG.4(b), the organic barrier layer (solid portion) 14 is formed in a ringshape around the particle P. Where the particle P has a diameter(equivalent circle diameter) of, for example, about 1 μm as seen in adirection normal to the surface of the OLED 3, the ring-shaped solidportion has a diameter (equivalent circle diameter) D₀ that is, forexample, longer than, or equal to, 2 μm. In the case of, for example, a5.7-inch display device having 2560×1440 pixels (about 500 ppi), thepixel pitch is 49 μm. The size of the particle P and the size of theorganic barrier layer (solid portion) 14 formed in the vicinity of theparticle P are sufficiently smaller than the pixel pitch. Therefore, achange in the transmittance caused by the organic barrier layer 14(solid portion) formed in the vicinity of the particle P does not have asignificant influence on the display.

The organic barrier layer 14 may be formed by, for example, the methoddescribed in Patent Document No. 1 or 2 mentioned above. For example, ina chamber, a vapor-like or mist-like organic material (e.g., acrylicmonomer) is supplied onto an element substrate maintained at atemperature lower than, or equal to, room temperature and is condensedon the element substrate. The organic material put into a liquid stateis located locally, more specifically, at the border between the sidesurface of the protruding portion of, and the flat portion of, the firstinorganic barrier layer 12 by a capillary action or a surface tension ofthe organic material. Then, the organic material is irradiated with, forexample, ultraviolet rays to form the solid portion of the organicbarrier layer (e.g., acrylic resin layer) 14 at the above-mentionedborder in the vicinity of the protruding portion. The organic barrierlayer 14 formed by this method does not substantially include the solidportion on the flat portion. Regarding the method for forming theorganic barrier layer, the disclosures of Patent Documents Nos. 1 and 2are incorporated herein by reference. During the formation, for example,the viscosity of the photocurable resin, and the wettability of thephotocurable resin to the inclining surface of the bank layer arecontrolled such that a liquid film is formed on the inclining surface.The surface of the inclining surface may be modified. The thickness ofthe resin layer to be formed first may be adjusted (e.g., to less than100 nm), and/or ashing conditions (including time) may be adjusted, toform the organic barrier 14.

In this example, the particles are present below the first inorganicbarrier layer 12. Also in the case where the particles are present abovethe first inorganic barrier layer 12, the organic barrier 14 including aplurality of solid portions distributed discretely only in discontinuousportions formed by the particles may be formed in substantially the samemanner.

In the case where the particle P has a size (sphere equivalent diameter)of generally 0.3 μm or longer and 5 μm or shorter, themoisture-resistance reliability of the TFE structure 10 is decreased.One OLED display device (active region) may include several particles Phaving such a size or may have no particle P. As described inPCT/JP2017/042913 applied by the present applicant, an organic barrierlayer including solid portions distributed discretely only indiscontinuous portions formed by the particles may be formed byink-jetting. A particle having a size exceeding 5 μm is removed bywashing or the like.

Namely, the step of forming the thin film encapsulation structurecovering a plurality of organic EL elements included in the elementsubstrate includes a step of forming the first inorganic barrier layer;a step of, after this step, detecting the particles below or above thefirst inorganic barrier layer to acquire position information on each ofthe particles; a step of, based on the acquired position information,attaching a microscopic liquid drop of a coating liquid containing aphotocurable resin to each of the particles by ink-jetting; a step of,after this step, irradiating the photocurable resin with ultravioletrays to cure the photocurable resin and thus forming the organic barrierlayer; and a step of, after this step, forming the second inorganicbarrier layer on the first inorganic barrier layer and the organicbarrier layer. A photocured resin layer formed by curing thephotocurable resin may be partially ashed.

An inkjet head that ejects microscopic liquid drops, each having avolume in the order of 1 fL (1 fL or larger and smaller than 10 fL) or avolume smaller than 1 fL is preferably usable. 1 fL corresponds to thevolume of a sphere having a diameter of about 1.2 μm, and 0.1 fLcorresponds to the volume of a sphere having a diameter of about 0.6 μm.For example, an inkjet device (Super Inkjet (registered trademark))produced by SIJ Technology Inc., capable of ejecting 0.1 fL microscopicliquid drops, is preferably usable. The entirety of the disclosure ofPCT/JP2017/042913 is incorporated herein by reference.

The organic barrier layer 14 may be formed by, for example, spraying,spin-coating, slit-coating, screen printing or ink-jetting. The methodfor forming the organic barrier layer 14 may further include an ashingstep. The organic barrier layer may be formed of a photocurable resinand exposed to light through a mask. The organic barrier layer may beexposed to light through a mask to form a pixel periphery solid portionand also to form an inorganic barrier layer joint portion, where thefirst inorganic barrier layer and the second inorganic barrier layer arein direct contact with each other.

The TFE structure is not limited to including the above-describedorganic barrier layer including the solid portions distributeddiscretely. The TFE structure may include a relatively thick organicbarrier layer (e.g., having a thickness of about 5 μm to about 20 μm)acting also as a flattening layer. The relatively thick organic barrierlayer is typically formed on the entirety of the active region byink-jetting. For example, a dam (wall) enclosing the entirety of theactive region is formed, and an organic material to be formed into theorganic barrier layer is provided by ink-jetting into the region definedby the dam (wall). The organic barrier layer formed on the entirety ofthe active region is enclosed by the inorganic barrier layer jointportion. The inorganic barrier layer joint portion is formed on, forexample, a side surface and/or a top surface of the dam (wall). In thecase where such a relatively thick organic barrier layer is formed, thefirst inorganic barrier layer may be omitted.

As the first inorganic barrier layer and the second inorganic barrierlayer, a silicon nitride (Si₃N₄) layer, which has a high level ofbarrier property, is preferably usable. It is especially preferred touse a silicon nitride layer having a refractive index of 1.80 or higherand 1.90 or lower. An SiO₂ layer, an SiON layer, an SiNO layer, an Al₂O₃layer or the like is usable instead of the Si₃N₄ layer.

As schematically shown in FIG. 6(a), the OLED display device 100according to an embodiment of the present invention further includes apolydiacetylene layer 52 selectively provided on the second inorganicbarrier layer 16 of the TFE 10 on the blue pixel and exhibiting a bluecolor. The polydiacetylene layer 52 exhibiting a blue color narrows thespectral width of blue light emitted by an organic light emitting layerin the blue pixel, and transmits the blue light at a high transmittance.Namely, the polydiacetylene layer 52 exhibiting a blue color improvesthe color purity of the blue color. For example, the polydiacetylenelayer 52 provides a transmission spectrum of the blue light in which theblue light has a peak wavelength (wavelength at which the transmittanceis highest) in a range of about 460 nm or longer and about 470 nm orshorter, and has a transmittance for the blue light higher than, orequal to, 80% at the peak wavelength. The polydiacetylene layer 52exhibiting a blue color may be provided, so that the color purity of theblue color, which is decreased by variance in the thickness of theorganic light emitting layer in the blue pixel, is suppressed fromdecreasing. By contrast, as schematically shown in FIG. 6(b), the greenpixel does not include the polydiacetylene layer 52. Like the greenpixel, the red pixel does not include the polydiacetylene layer 52either.

The polydiacetylene layer 52 exhibiting a blue color is a polymer, of10, 12-pentacosadiynoic acid.

The polydiacetylene layer 52 is formed as follows, for example.

After the second inorganic barrier layer 16 of the TFE structure 10 isformed, 10, 12-pentacosadiynoic acid (hereinafter, referred to simply as“PCDA”) is deposited by, for example, mask vapor deposition on thesecond inorganic barrier layer 16 without exposing the second inorganicbarrier layer 16 to the atmosphere. PCDA is deposited in the state wherethe vacuum degree in the chamber is set to, for example, lower than, orequal to, 10⁻³ Pa and the temperature of the second inorganic barrierlayer 16 is maintained at, for example, 50° C. The vacuum vapordeposition is used to deposit PCDA because in this manner, a film havinga relatively high degree of orientation is provided. From the point ofview of the degree of orientation, it is preferred that the underlyinglayer is an SiN layer.

After this, PCDA is irradiated with an electron beam or ultraviolet;rays (e.g., 250 μm or shorter) to polymerize PCDA. As a result, thepolydiacetylene layer 52 is obtained. The transmission spectrum throughthe polydiacetylene layer 52 may be adjusted by the irradiationconditions (intensity and time) of the electron beam or the ultravioletrays. The relationship between the irradiation conditions and thetransmission spectrum may be found in advance regarding the electronbeam or the ultraviolet ray to be used, so that a polydiacetylene layerproviding an intended transmission spectrum is obtained easily. It ispreferred that the polydiacetylene layer 52 has a thickness of, forexample. 0.5 μm or greater and 2.0 μm or less.

In the case where the electron beam is used to polymerize PCDA, thepolymerization may be performed with a polymerization device. Thepolymerization device has, in a vacuum chamber, a cathode (electron gun)and a focusing coil that provide the electron beam, and a polarizingcoil at one side, and a stage acting as an anode at the other side. Asubstrate on which the OLED display device 100 is formed is transportedinto the polymerization device and set on the stage. After this, thesubstrate is scanned with the electron beam. In this manner, thepolymerization is performed. Instead of the stage, the upper electrode46 of the OLED display device 100 may be used as the anode. From thepoint of view of the mass-productivity and the cost, it is morepreferred to use an ultraviolet irradiation device for thepolymerization.

PCDA is of a chemical formula C₂₅H₄₂O₂ and has a molecular weight of374.60. Formula 1 is the structural formula of PCDA.

For example, the red pixels in the OLED display device 100 emit lighthaving a wavelength of 600 nm or longer and 690 nm or shorter. The greenpixels emit light having a wavelength of 500 nm or longer and 590 nm orshorter. The blue pixels emit light having a wavelength of 400 nm orlonger and 490 nm or shorter.

In order to discuss the color reproducibility, the DCI (Digital CinemaInitiatives) specifications and the sRGB specifications will be comparedagainst each other. Specifically, the chromaticity coordinates of theblue pixels are the same in both of the specifications. Namely, it isimportant that the chromaticity coordinates of the blue pixels should bewithin the range of desirable values (x=0.150, y=0.060, peakwavelength=about 460 nm or longer and about 470 nm or shorter).

However, in an OLED display device, especially, in an OLED displaydevice having a microcavity structure, the wavelength of light emittedby the blue pixels may undesirably be out of the above-mentionedwavelength range due to variance in the thickness of the organic ELlayer (e.g., organic light emitting layer). The polydiacetylene layer 52described above absorbs the light that is out of the above-mentionedwavelength range and transmits such blue light at a high transmittance.Therefore, the wavelength of the light emitted by the blue pixels iswithin a desired range regardless of the thickness of the organic ELlayer. As a result, an OLED display device having an improved colorpurity of the blue pixels regardless of the production variance of theOLED display device is produced.

When ultraviolet rays are incident on the polydiacetylene layer 52, thepolymerization degree (conjugated chain length) may undesirably bechanged to change the transmission spectrum. Therefore, under certainuse environments of the OLED display device 100, it is preferred toprovide an ultraviolet absorbing layer on the polydiacetylene layer 52.The ultraviolet absorbing layer may be a known layer such as, forexample, a titanium oxide layer or the like. In the case where, forexample, the OLED display device 100 includes a circular polarizingplate, a material absorbing ultraviolet rays may be used for a resinlayer included in the circular polarizing plate.

In the case where mask vapor deposition is used, the polydiacetylenelayer 52 may be formed selectively only on the blue pixels. Thepolydiacetylene layer 52 is not limited to being formed in this manner.A solution of PCDA may be used to form the polydiacetylene layer 52selectively only on the blue pixels by ink-jetting. The solution has aconcentration of, for example, 0.1% by mass. The rate at which thesolvent is removed may be adjusted, so that the polydiacetylene layer 52having a high degree of orientation is obtained. There is no specificlimitation on the solvent usable for the PCDA solution. Usable solventsinclude tetrahydrofuran, toluene, xylene, dioxane, chloroform,dichloromethane, etc., and a mixed solvent thereof. The volumetric ratio(partial pressure) of the solvent vapor with respect to the atmosphereof the element substrate supplied with the PCDA solution may beadjusted, so that the rate at which the solvent is removed is adjusted(see, for example, Japanese Laid-Open Patent Publication No.2009-224620).

A liquid crystal display device or the like uses an insulating colorfilter, whereas the polydiacetylene layer 52 is semiconductive andtherefore, is difficult to be charged. The voltage applied to cause theblue pixels to emit light is higher than for the other colors of pixels.Therefore, the blue pixels are especially easily chargeable. Theprovision of the polydiacetylene layer 52 provides an effect ofsuppressing the blue pixels from being charged. In addition, themeasures against electrostatic discharge (ESD) may be omitted oralleviated. It is preferred that the polydiacetylene layer 52 has aspecific resistance smaller than, or equal to, 1×10⁻¹ Ωcm.

INDUSTRIAL APPLICABILITY

An embodiment of the present invention is applicable to an organic ELdisplay device, specifically, a flexible organic EL display device, anda method for producing the same.

REFERENCE SIGNS LIST

-   1 substrate (flexible substrate)-   2 circuit-   3 OLED layer-   4 polarizing plate-   10 TFE structure-   12 first inorganic barrier layer (SiN layer)-   14 organic barrier layer-   14 a pixel periphery solid portion-   16 second inorganic barrier layer (SiN layer)-   30 lead wire-   38 terminal-   42 lower electrode-   44 organic layer-   46 upper electrode-   48 bank layer-   52 polydiacetylene layer-   100 OLED display device-   BS bank structure-   P particle-   Pix pixel-   R1 active region-   R2 peripheral region

The invention claimed is:
 1. A method for producing an organicelectroluminescent display device including a plurality of pixels, theorganic electroluminescent display device comprising: an elementsubstrate including a substrate, a plurality of organicelectroluminescent elements supported by the substrate and respectivelylocated in the plurality of pixels, and a bank layer defining theplurality of pixels; and a thin film encapsulation structure coveringthe plurality of pixels, wherein: the thin film encapsulation structureincludes a first inorganic barrier layer and an organic barrier layer incontact with a top surface or a bottom surface of the first inorganicbarrier layer; the plurality of pixels include a red pixel having anelectroluminescent element that emits only red light, a green pixelhaving an electroluminescent element that emits only green light and ablue pixel having an electroluminescent element that emits only bluelight; the organic electroluminescent display device further includes apolydiacetylene layer selectively provided only on the thin filmencapsulation structure on the blue pixel and exhibiting a blue color,and the polydiacetylene layer is a polymer of 10, 12-pentacosadiynoicacid; forming the polydiacetylene layer comprises: after the thin filmencapsulation structure is formed, depositing 10, 12-pentacosadiynoicacid on the thin film encapsulation structure by mask vapor deposition;and irradiating the 10, 12-pentacosadiynoic acid with an electron beamor ultraviolet rays; forming the thin film encapsulation structurecomprises: preparing, in a chamber, the element substrate on which thefirst inorganic barrier layer is formed; supplying a vapor-like ormist-like photocurable resin into the chamber; condensing thephotocurable resin on the first inorganic barrier layer to form a liquidfilm; irradiating the liquid film of the photocurable resin with lightto form a photocured resin layer; and partially ashing the photocuredresin layer to form the organic barrier layer.
 2. The method of claim 1,wherein forming the thin film encapsulation structure further comprises:forming a silicon nitride layer; and after the silicon nitride layer isformed, depositing the 10, 12-pentacosadiynoic acid by the mask vapordeposition without exposing the silicon nitride layer to the atmosphere.3. The method of claim 1, wherein: the organic barrier layer included inthe thin film encapsulation structure is in contact with the top surfaceof the first inorganic barrier layer and includes a plurality of solidportions distributed discretely; the thin film encapsulation structurefurther includes a second inorganic barrier layer in contact with thetop surface of the first inorganic barrier layer and top surfaces of theplurality of solid portions of the organic barrier layer; and thepolydiacetylene layer is formed on the second inorganic barrier layer.4. The method of claim 1, wherein the polydiacetylene layer issemiconductive.
 5. The method of claim 1, wherein the polydiacetylenelayer has a specific resistance smaller than, or equal to, 1×10⁻¹ Ωcm.6. The method of claim 1, wherein the organic electroluminescent displaydevice further comprises an ultraviolet absorbing layer located on thepolydiacetylene layer.
 7. The method of claim 1, wherein the firstinorganic barrier layer is formed of silicon nitride.
 8. The method ofclaim 1, wherein the polydiacetylene layer has a thickness of 0.5 μm orgreater and 2.0 μm or less.
 9. The method of claim 1, wherein thepolydiacetylene layer provides a transmission spectrum of blue light inwhich the blue light has a peak wavelength in the range of 460 nm orlonger and 470 nm or shorter.
 10. The method of claim 1, wherein thepolydiacetylene layer has a transmittance for the blue light higherthan, or equal to, 80% at the peak wavelength thereof.